The present invention relates to structure stabilizing systems, and more particularly to a vibration damping system for removing vibrations from a structure over a fairly wide range of frequencies of vibration.
Vibration has historically been recognized as a problem which can produce a variety of adverse effects in equipment. Special precautions are needed to protect machine elements of air-borne laser tracking systems. One such system while mounted on an optical bench in a U.S. Air Force laser lab aircraft experienced beam jitter induced by vibration that was so strong, that the conical tracking loop would break lock.
The task of damping such undesirable vibration in the structure of the optical bench, while minimizing the impact on the existing design, has been alleviated, to some extent, by the following U.S. patents, which are incorporated herein by reference:
U.S. Pat. No. 2,443,471 issued to Mason on 15 June 1948; PA0 U.S. Pat. No. 2,964,272 issued to Olson on 13 Dec. 1960; PA0 U.S. Pat. No. 3,464,657 issued to Bullard on 2 Sept. 1969; and PA0 U.S. Pat. No. 3,703,999 issued to Forys et al on 28 Nov. 1972.
All of the references cited above disclose systems for controlling mechanical vibration. The Mason reference discloses a damping assembly which uses a pair of piezoelectric crystal plates as a damping means. The approach of applying dynamically responsive damping elements is superior to mechanical mounting solutions such as springs, dash pots and other vibration absorbing mountings. However, the present problem also requires removing vibration over a wide range of frequencies.
The Olson and Bullard references provide a vibration controlling apparatus containing a vibration sensing element, an amplifier, and a driving element. The driving element translates the amplified electrical signal into mechanical force to compensate for vibration. The present problem requires a vibration damping system capable of responding to components of vibration produced by both acceleration as well as velocity of the host aircraft and neither of the above-cited references accomplish both velocity and acceleration nulling.
The Forys et al reference discloses a wideband stabilizing system for stabilizing cameras on moving vehicles. This stabilizing system includes a mounting system which houses the camera, as well as damps motion induced vibration. However, for the present problem, it is preferred to use the existing optical bench, rather than construct a new platform. Therefore, a vibration damping system is needed which may be attached to existing structures.